Precursor composition for solid electrolyte, and method for producing secondary battery

Abstract

A precursor composition for a solid electrolyte is provided that is capable of achieving a high lithium ion conductivity even if the precursor composition is sintered at a temperature of 1000° C. or lower. The precursor composition for the solid electrolyte is a precursor composition for a garnet-type or garnet-like solid electrolyte containing Li, La, Zr, and M, wherein the M is one or more types of elements selected from Nb, Ta, and Sb, the compositional ratio of Li:La:Zr:M in the solid electrolyte is 7-x:3:2-x:x, a relationship of 0<x<2.0 is satisfied, and the precursor composition exhibits X-ray diffraction intensity peaks at diffraction angles 2θ of 28.4°, 32.88°, 47.2°, 56.01°, and 58.73° in an X-ray diffraction pattern.

1 . A precursor composition for a solid electrolyte, which is a precursor composition for a garnet-type or garnet-like solid electrolyte containing Li, La, Zr, and M, wherein
 the M is one or more types of elements selected from Nb, Ta, and Sb,   the compositional ratio of Li:La:Zr:M in the solid electrolyte is 7-x:3:2-x:x, and a relationship of 0<x<2.0 is satisfied, and   the precursor composition exhibits X-ray diffraction intensity peaks at diffraction angles 2θ of 28.4°, 32.88°, 47.2°, 56.01°, and 58.73° in an X-ray diffraction pattern.   
     
     
         2 . The precursor composition for a solid electrolyte according to  claim 1 , wherein the precursor composition for a solid electrolyte contains nitrate ions. 
     
     
         3 . The precursor composition for a solid electrolyte according to  claim 1 , wherein the M is two or more types of elements selected from Nb, Ta, and Sb. 
     
     
         4 . A method for producing a secondary battery, comprising:
 a step of forming a solid electrolyte layer by forming a molded material using the precursor composition for a solid electrolyte according to  claim 1 , and sintering the molded material;   a step of forming a positive electrode at one face of the solid electrolyte layer;   a step of forming a negative electrode at the other face of the solid electrolyte layer; and   a step of forming a current collector in contact with at least one of the positive electrode and the negative electrode.   
     
     
         5 . A method for producing a secondary battery, comprising:
 a step of forming a positive electrode composite material by forming a molded material including the precursor composition for a solid electrolyte according to  claim 1  and a positive electrode active material, and sintering the molded material;   a step of forming a negative electrode at one face of the positive electrode composite material; and   a step of forming a current collector at the other face of the positive electrode composite material.   
     
     
         6 . A method for producing a secondary battery, comprising:
 a step of forming a negative electrode composite material by forming a molded material including the precursor composition for a solid electrolyte according to  claim 1  and a negative electrode active material, and sintering the molded material;   a step of forming a positive electrode at one face of the negative electrode composite material; and   a step of forming a current collector at the other face of the negative electrode composite material.   
     
     
         7 . A method for producing a secondary battery, comprising:
 a step of forming a sheet of a positive electrode composite material mixture including a first precursor composition for a solid electrolyte and a positive electrode active material;   a step of forming a sheet of a negative electrode composite material mixture including a second precursor composition for a solid electrolyte and a negative electrode active material;   each of the first and second precursor compositions being the precursor composition for the solid electrolyte according to  claim 1 ;   a step of forming a sheet of an electrolyte mixture including a solid electrolyte;   a step of forming a stacked body by stacking the sheet of the positive electrode composite material mixture, the sheet of the electrolyte mixture, and the sheet of the negative electrode composite material mixture in this order;   a step of forming a molded material by molding the stacked body;   a step of firing the molded material; and   a step of forming a current collector at at least one face of the fired molded material.   
     
     
         8 . The method for producing a secondary battery according to  claim 7 , wherein the solid electrolyte is formed using a precursor composition for a garnet-type or garnet-like solid electrolyte containing Li, La, Zr, and M, wherein
 the M is one or more types of elements selected from Nb, Ta, and Sb,   the compositional ratio of Li:La:Zr:M in the solid electrolyte is 7-x:3:2-x:x, and a relationship of 0<x<2.0 is satisfied, and   the precursor composition exhibits X-ray diffraction intensity peaks at diffraction angles 2θ of 28.4°, 32.88°, 47.2°, 56.01°, and 58.73° in an X-ray diffraction pattern.